Flow and heat transfer characteristics of ammonium alum hydrate slurries

Flow and heat transfer characteristics of ammonium alum hydrate slurries have been investigated. Ammonium alum hydrate has high latent heat of 251 kJ kg−1 and its melting temperature is 51 °C when the concentration of ammonium alum in water was set at 35 wt%. The friction and the melting heat transfer coefficients were measured in a pipe flow with 13 mm of diameter. From the results, it was found that the friction coefficient of ammonium alum hydrate slurry shows almost the same value as that of water. On the other hand, the slurry shows higher heat transfer than that of water. Especially, the heat transfer enhanced rate becomes high when the temperature difference between the slurry and the heating flow was set small. This is because of the temperature sustainability of phase change material slurries. From this, it was concluded that ammonium alum hydrate slurry can be a promising candidate for a heating system.